Current Trends
Mumps -- United States, 1985-1988

After the introduction of live mumps virus vaccine in 1967 and the
recommendation for its routine use in 1977, the incidence rate of
reported mumps cases in the United States decreased steadily. In
1985,
a record low of 2982 cases occurred, representing a 98.0% decline
from
the 152,000 cases reported in 1968 (Figure 1). However, from 1985
to
1987, mumps increased; 7790 and 12,848 cases were reported in 1986
and
1987, respectively. During this time, the annual reported incidence
rate rose almost fivefold, from 1.1 cases/100,000 population to 5.2
cases/100,000 population (Table 1). However, in 1988, a provisional
total of 4730 cases was reported, representing a 63.2% decrease
from
1987.

In 1987, of the 48 areas (47 states plus the District of Columbia)
that routinely reported mumps cases, at least one mumps case was
reported from all but three (Delaware, Rhode Island, and Wyoming)
of
the reporting areas. Similarly, in 1988, all except Maine, North
Dakota, and Rhode Island have provisionally reported mumps cases.
In
1985, seven states (Illinois, Tennessee, Michigan, Wisconsin,
Indiana,
Louisiana, and Minnesota) reported more than 500 cases each (case
range: 810-2737, incidence range: 18.1-37.7 cases/100,000
population).
In addition, in 1985, 680 (22.8%) of the 2982 counties in the 48
reporting areas reported at least one case, compared with 889
(28.3%)
of 3138 in 1987. During 1987, 31 (64.6%) of the 48 reporting areas
noted more mumps cases than in 1986.

Final age-specific data are available through 1987 (Table 1). Most
(55.2%) mumps cases reported in 1987 occurred in school-aged
children
(5-14 years of age). For comparison, an average of 74.6% of
reported
cases occurred in this age group between 1967 and 1971 (the first
5-year period postlicensure). However, whereas an annual average of
8.3% of reported cases were among persons greater than or equal
to15
years of age in 1967-1971, this age group accounted for 38.3% of
the
reported total in 1987. Although reported mumps incidence increased
in
all age groups from 1985 to 1987, rates increased most
substantially
among 10-14-year-olds (almost a sevenfold increase) and
15-19-year-olds
(over an eightfold increase) (Table 1). For the first time since
mumps
became a reportable disease, the reported peak incidence rate
shifted
for 2 consecutive years from 5-9-year-olds, the age group
traditionally
associated with the highest risk of disease (1,2), to older age
groups.
The increased occurrence of mumps in susceptible adolescents and
young
adults has been demonstrated in several recent outbreaks on college
campuses (3) and in occupational settings (4). Nonetheless, despite
this age shift in the epidemiology of reported mumps, the overall
risk
of disease in persons 10-14 and greater than or equal to15 years of
age
is still lower than that in the prevaccine and early postvaccine
licensure periods.

Reported incidence rates continue to be affected by school
immunization laws (5). For example, in the 15 areas (14 states and
the
District of Columbia) that had comprehensive (i.e., kindergarten
through grade 12 (K-12)) laws requiring proof of immunity against
mumps
for school attendance, the incidence rate in 1987 was 1.1 mumps
cases/100,000 population (Table 2). In contrast, mumps incidence
was
highest in the 14 states routinely reporting mumps cases in 1987
that
had no requirements for mumps vaccination (11.5 cases/100,000
population) and intermediate (6.2 cases/100,000 population) in the
18
states with partial vaccination requirements for school attendance
(i.e., those that include some children but do not comprehensively
include K-12) that routinely reported cases. All states that had
greater than 500 reported cases in 1987 had either no or partial
school
immunization requirements. Provisional 1988 data suggest this trend
is
continuing, with incidence rates of 1.4/100,000 in states with K-12
laws in effect at the beginning of that year, 1.9/100,000 in states
with partial requirements in effect at the beginning of that year,
and
3.2/100,000 in states with no school immunization laws in effect at
the
beginning of that year.

The shift in age-specific risk noted above occurred only in states
without comprehensive K-12 school vaccination requirements. Mumps
incidence in 1987 decreased substantially in preschool- and
school-aged
children, even in the absence of any school laws;
however, the reported incidence rates for 10-14-year-olds in
states
with no laws (65.5 cases/100,000 population) approached 1967-1971
levels (75.5 cases/100,000 population) (Figure 2). For persons
greater
than or equal to15 years of age in such states, the reported rates
were
equivalent to reported 1967-1971 rates (both at 5.8 cases/100,000
population).
Reported by: Div of Immunization, Center for Prevention Svcs, CDC.

Editorial Note

Editorial Note: Through 1987, more than 82.3 million doses of
live
mumps virus vaccine were distributed in the United States. The
principal strategy to control mumps in the United States is to
achieve
and maintain high immunization levels, primarily among infants and
young children. The Immunization Practices Advisory Committee of
the
Public Health Service recommends that universal mumps immunization
routinely should be carried out in physicians' offices and public
health clinics in all communities; trivalent measles-mumps-rubella
(MMR) vaccine is the vaccine formulation of choice (6). This
strategy
is also cost-effective (7,8). Unless otherwise contraindicated, all
persons thought to be susceptible should be vaccinated. Susceptible
persons include those without documentation of 1)
physician-diagnosed
mumps, 2) immunization with live mumps virus vaccine at greater
than or
equal to12 months of age, or 3) laboratory evidence of immunity.

Ensuring immunity for adolescents and young adults is especially
important, given the recent shift in risk of disease to these age
groups. This trend does not appear to be due to waning immunity in
persons vaccinated previously and is probably attributable to the
relatively underimmunized cohort of children born between 1967 and
1977
(9). The evidence that the shift in risk to older persons through
1987
is limited to states without comprehensive mumps immunization
school
laws provides further evidence that the relative resurgence of
mumps in
the United States is not due to vaccine failure but to a failure to
vaccinate.

Although seroepidemiologic surveys, especially of adolescents and
young adults, are needed to better define the magnitude and extent
of
susceptible cohorts, several actions are necessary to decrease the
pool
of susceptibles and to ensure that high rates of immunization are
maintained. The adoption and enforcement of universal comprehensive
vaccination requirements for school attendance are likely to reduce
mumps incidence substantially. At the end of 1988, 17 states and
the
District of Columbia had comprehensive K-12 laws in effect, 18
states
had partial vaccination requirements, and 15 states had no
requirements
for mumps vaccination (Figure 3). Tennessee and Illinois, which
together accounted for 57% and 31% of the total number of reported
U.S.
mumps cases in 1986 and 1987, respectively, have recently enacted
comprehensive K-12 requirements. Similar requirements in colleges,
as
recommended by the American College Health Association (10), and
selected places of employment should also be considered; selected
places of employment where persons in this age cohort are likely to
be
concentrated or where the consequences of disease spread may be
more
severe (e.g., medical-care settings) would help focus attention on
groups that appear to be at highest risk. More aggressive outbreak
control, including exclusion of susceptibles from school, is also
helpful in eliminating transmission in mumps epidemics.

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